Switch devices



Aug. 25, 1959 R. L. SNYDER, JR

SWITCH DEVICES Filed May 12, 1954 5 Sheets-Sheet 2 INVENTOR.

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SWITCH DEVICES 5 Sheets-Sheet 3 Filed May 12, 1954 INVENTOR. jzfiaxjj 5yj? g- 1959 R. L. SNYDER, JR 2,901,731

swncu DEVICES United States Patent SWITCH DEVICES Richard L. Snyder,Jr., Moorestown, NJ.

Application May 1-2, 1954, 'Serial No. 429,351 3 Claims. 01. 340 174This invention relates to electrical switches and selectors forcontrolling the passage of electrical energy between two'pairs ofcircuit terminals or between one pair of terminals and a selected pairof a plurality of other pairs of terminals. It relates particularly-toswitches and selectors-utilizing reactance elements with saturablemagne'tic cores, the saturation of which can be controlled at will. Theswitches and selectors of the present invention comprise networks ofsuch reac'tance elements, so controllable as to permit or prevent atwill the transmission of electrical energy through a single switch andto permit such transmission through a selected path of a plurality ofalternate paths between input and output terminals of a selector.

Transmission of electrical energy between pairs of terminals of aswitching or selector device or non-transmission thereof, isconventionally controlled by mechanically moving metallic contacts,thereby to make or break metallic conductive connections. Such contactsare usually parts of electromagnetic relay-s. Since such devices employmechanical motion and mechanical members with mass, they are notsuitable for extremely rapid operation, such as required for example, inmodern electronic computers. Moreover, they are subject to considerablewear and tear, making frequent replacement necessary when used inselector systems in which rapid and frequentswitching must take place.

Selector systems have been devised using electronic tubes as switchingdevices. Such systems are not suitable, however, to handle a wide rangeof power levels of signals. Some modern computers, for example, requireselector systems capable of reliable operationover a powerrange in theorder of 105 to-one or greater; 7

Switchesand'selectors, hitherto devised using 's-a'turablecore reactanceelement's, do not provide 'suflici'ent' discrimination, that is, theratio of energy transmitted for the-saturated and unsaturated conditionsof the core, respectively, is not sufficiently great to fill the needsof modern equipment, such as some "automatic computing machines.

An objectof this invention, therefore, is to provide electricalswitdiing and selecting devices adapted for extremely rapid operationand for extremely wide control of the degree of transmission ornon-transmission of electrical energy.

- A further object of this invention is to provide switching andselector systems capable of reliable and noisefree operation over arange of electrical energy transmitted of about to one, or greater.

' Another object o f the invention is to provide a switching, system inwhich the inductance values of a plurality of controlled windings intransmission paths of electrical energy are controlled by the electricalcurrent through a single associated control winding.

The'various features of novelty which characterize my invention arepointed out withparticularity in the claims annexed to and forming apart of this specification. For

Patented Aug. 25 i 1 959 ice a better understanding of the invention,its advantages, and specific objects attained by its use,reference's'hould be had to the accompanying drawingsand descriptivematter, in which -I have illustrated and described preferred embodimentsof my invention.

Of the drawings:

Fig. 1 shows a basic saturabl'e reactor structure;

Fig. 2 shows a similar structure with modified controlled winding; 7 I 1Fig. 3 shows'a schematic representation of Fig. -1

Fig. 4 illustrates a reactor structure with a single control winding andseveral simultaneously controlled'windings;

Fig. 5 shows a schematic representation of the reactor of Fig. 4'; v I

Fig. 6 schematically illustrates a. switch in accordance with thepresent invention;

Fig. 7 schematically illustrates a similar sw-itchwith with a higherdegree of discrimination between on and off positions;

Fig. 8 schematically shows a novel selector system;

Fig. 9 schematically shows a novel binary selector system used inconjunction with a memory device for automatic computing machines;

Fig. 10 schematically shows a selector similar to Fig. 8 with a greaternumber of alternate transmission paths;

Fig. 11 schematically shows 'a novel selector system for use in adecimal-type system;

Fig. 12 schematically shows a novel selector system for binaryoperation; and

Fig. 13 schematically shows a modification of the system of Fig. 12.

Fig. 1 shows a reactor element having a magnetic core 1 of relativelyeasily saturable material, such as certain types of laminated iron orso-called ferrite's. The core is of substantially uniform cross section,except at 2', where it is provided with a window, leaving two magneticpaths of greatly reduced cross sections that can be saturated relativelyreadily. A control winding 3 is pro.- vided for'saturating the narrowcore sections at 2, when an electrical current is passed through thewinding. A controlled winding 4 is wound around the two core sections at'2 as shown, in such directions, that a change in' magnetic fluxgenerated by current passing through winding 4- causes voltages todevelop across each coil of the Winding in an additive fashion, andequal voltages of opposite phase are induced in winding 4 that canceleach other when changing magnetic flux is generated by Winding 3.Consequently, no net voltage is induced in winding ,4 from winding 3.Conversely, the same holds true.

It is well known, that under the above conditions, the inductivereactance of the controlled winding 4 decreases considerably when thecore at '2 is saturated. In practice, I have found that inductancechanges of the order of to l are attainable from unsaturated tosaturated condition of the core sections at 2.

From Fig. 1, it is seen that, in the absence of'current through controlwinding 3, the two portions of the controlled winding 4 circulate theirflux about the window at 2, a's'indicated by 'the'arrows. No flux islinked with control winding 3.

When control winding 3 'is fully excited and the core sections at 2saturated, the flux in one section produced by the current through thecontrolled winding 4 opposes the flux produced by control Winding 3. Theopposing flux, which must be overcome, can. be appreciable, because forsaturated conditions the current through the controlled winding becomesgreatest as its impedance diminishes;

Fig. 2 shows a different type of controlled winding 4a on a structureotherwise substantially identical to that of Fig. 1. In this arrangementthe two sections of the controlled winding are connected aidingparallel, so that their flux does not link with the control winding (notshown). When current is passed through the control winding to saturatethe core structure, no appreciable voltage can be developed across oneof the parallel sections of controlled winding 4a, because this wouldrequire the flux to increase further in the saturated direction.Therefore, to produce minimum 'reactance of the controlled winding,current in the controlled winding does not require higher flux from thecontrol winding for saturation. of the core, as it does for thearrangement of Fig. 1. However, this type of controlled winding has thedisadvantage of developing a short circuit when the control windingcurrent is rapidly changed, thus preventing sufficiently rapid change incontrolled 'winding inductance to make this arrangement satisfactory forvery high speed operation.

My invention is not limited to the use of one or the other of thesetypes of controlled windings, since either can be used, the choicedepending upon the ultimate application of the switch or selector systemin which such reactor elements are to be used.

Fig. 3 shows a schematic representation of reactor elements of Figs. 1and 2. Core 1 is represented by short parallel lines indicating asaturable core. Control winding 3 and controlled winding 4 are drawn atright angles to each other, signifying that there is no flux linkagebetween the two windings.

Fig. 4 shows a basic reactor structure having a sat-urable core 1, asectionalized control winding 3, a plurality of core openings indicatedat 2, and four separate controlled windings 4. Fig. 5 is a schematicrepresentation of such a structure.

I have found that a suitable reactor can be made, as shown in Fig. 4,using a cylindrical ferrite core, having a length of one inch, an outerdiameter of 0.62 inch, and an inner diameter of 0.430 inch. The openingsshown at 2 in Fig. 4 extend over the entire cylinder length and have adiameter of 0.05 inch. The number of openings depends upon the number ofcontrolled windings to be controlled by a single control winding. In theexample cited twelve holes are used. By way of example, the controlledwindings may have from fourteen to twenty-eight turns, and the controlwinding one hundred and forty turns.

Fig. 6 shows a circuit diagram of a switch according to my invention. Itcomprises two saturable reactor elements 10:: and 10b, each havingsaturable magnetic cores 11a and 11b, control windings 12a and 12b, andcontrolled windings 13a and 13b. The controlled windings are connectedbetween two pairs of terminals 14 and 15. Winding 13a is connected inseries between two corresponding terminals of pairs 14 and 15, whereaswinding 13b is connected in parallel relation to terminal pair 15.

Control windings 12a and 12b are connected in an energizing circuit,shown by way of illustration of principle only, comprising a battery 16and a switch 17. Examples of practical circuit arrangements will bedescribed later.

In operation, control windings 12a and 12b are selectively energized byswitch 17 and battery 16. In the switch position shown, winding 12a isenergized, saturating core 11a to minimize the inductive reactance ofcontrolled winding 13a. No current flows through control winding 12b andthe inductive reactance of controlled winding 13b has its maxitmumvalue.

With minimum series impedance and maximum shunt impedance, transmissionof electrical energy between terminal pairs 14 and is least impeded.

When switch 17 is thrown to the right-hand position, control winding 12abecomes deenergized and winding 12b energized, so that the inductivereactance of controlled winding 13a assumes its maximum value, and

4 the reactance of 13b a much lower value. With a high series impedanceand low shunt impedance, minimum transmission between terminal pairs 14and 15 is effected.

The difference between maximum and minimum transmission with this novelswitch is considerably greater than with saturable magnetic deviceshitherto known, since those use single controlled windings only, insteadof a network thereof. Increased discrimination between maximum andminimum transmission can be obtained by other networks, as shown below.The source of energy can be connnected to either the terminal pairs 14or 15 and a receiver to the opposite pair, or transmission of energy canbe eifected selectively in either direction, as will be shown later.

Fig. 7 shows a switch similar to that of Fig. 6, except that it utilizesa network capable of greater discrimination in that it employs twoseries and two shunt inductances. Again there are provided two saturablereactor elements 20:: and 20b having cores 21a and 2117, respectively,control windings 22a and 22b, and controlled windings 23a, 24a, and 23band 241). Control windings 22a and 22b are connected to a source ofcurrent 27 by way of a switch 28. V

For the switch position shown, winding 22a is energized and controlledwindings 23a and 24a are at their minimum inductance value because ofsaturation of core 20a. Controlled windings 23b and 24b have theirmaximum inductance value, since control winding 22b is deenergized andcore 21b unsaturated. For this condition, minimum series inductancevalues and maximum shunt inductance values, maximum transmission ofenergy between terminal pairs 25 and 26 can take place.

When switch 28 is turned to the right-hand position, then maximum seriesand minimum shunt inductance values obtain and minimum transmissionbetween terminal pairs 25 and 26 can take place.

Fig. 8 shows a selector for selectively connecting one pair of firstterminals to one of two pairs of second terminals by greatly increasingthe degree of transmission between these pairs of terminals, whilesimultaneously reducing to a minimum the transmission between the firstterminals and the other pair of second terminals.

Accordingly, there are provided two saturable reactor elements 30a and30b, with control windings 31a and 31b, saturable cores 32a and 32b, andcontrolled windings 33a, 34a, 35a and 33b, 34b and 35b, as shown. Thecontrolled windings are connected in networks between terminal pairs 36,37 and 38, so that windings 33a and 34a are in series between terminals36a and 37b, and 33b connected between the junction of 33a and 34a andtenninals 36b and 37a, the latter being conductively connected as shown.Controlled windings 34b and 35b are connected in series betweenterminals 36a and 38b, whereas 35a is connected between the junction of34b and 35b and terminals 36b and 38a, the latter being conductivelyconnected.

In operation, assume control winding 31a to be energized, core 30asaturated, while control winding 31b is deenergized and core 30bunsaturated. In this condition, the inductance values of series windings33a and 34a is very low, whereas that of shunt winding 33b is very high,permitting maximum transmission of energy between terminal pairs 36 and37. Conversely, the inductance values of series windings 33b and 34b isvery high, whereas that of shunt winding 35a is very low, permittingminimum transmission of energy between terminal pairs 36 and 38. Hence,terminal pair 36 is efiectively connected to terminal pair 37 andeffectively disconnected from terminal pair 38.

In one embodiment of my invention, I found extremely effectivediscrimination to be obtained when varying windings 33a and 34b from 10to 2000 micro-henries, 34a and 35b from 5 to 1000 micro-henries, and 35aand 33b from 20 to 4000 micro-henries, from saturated to unsaturatedcondition of the cores.

asomsi Obviously, energy can be equally well transmitted selectivelyfrom 36 to either 37 or 38, or .from either 37 or 38 to 36. Since thesenetworks are bi-directional and this quality is made use of inaccordance with my invention, I have avoided the use of the terms .inputand output terminals, since the same terminals are used in shortsuccession in both capacities, as will be pointed out in connection withFig. 9.

Fig. 9 shows the schematic circuit diagram of an embodiment of my novelselector system used in conjunction with an automatic computing machine.In such machines it is necessary to store intermediate solutions of aproblem for later use by the machine. The information is often .storedin the form of magnetic patterns in a relatively high coercive forceterm-magnetic surface of a rotating drum produced by positive andnegative current pulses in windings on magnetic recording headspositioned close to the magnetizable surface of the drum. These pulsesmay have a duration in the order of between 0.2 and microseconds, spacedin time by intervals in the order ofbetween 3 and 30 microseconds. v

This circuit includes a recording amplifier, generally indicated at 40,adapted to receive from part of a computer (not shown) pulses toterminals 41 and'42, indicative of one or zero as is conventional inbinary computing machines. Such pulses produce current pulses of onedirection or opposite direction in a transformer secondary winding 43,applied to terminal pair 44 of my selector system. One of the functionsof the selector is to connect selectively terminals 44 to one of fourmagnetic recording and reproducing heads 45, 46, 47 and 48 cooperatingwith a magnetic drum 49, driven by a motor 50, for recording pulsesreceived at 41 and 42 on one of the four tracks on drum 49.

Another function of the selector system is to disconnect the heads 45,46, 47 and 48 from terminals 44 and connect a selected one to terminals51, connected to a reproducing amplifier generally indicated at 52. Theoutput of this amplifier at terminals 53, is applied to a portion of thecomputer (not shown) requiring the stored information.

Selection of recording or reproducing of information and selection ofthe specific magnetic head is effected by the program section of thecomputer, generally indicated at 54, transmitting properly timed pulsesof proper polarity to the control grids of tubes 55, 56, 57, 58, 59 and60, whose anodes are connected to control windings and to a commonbattery 61.

The selector system comprises three sections 62, 63 and 64, each withtwo saturable reactor elements. Sections 62 and 63 are the same as shownin Fig. 8 and described in connection therewith. When program section 54places a positive voltage on the control grid of tube 56 and a negativevoltage on the grid of tube 55, terminals 44 and 65 are connected andterminals 51 disconnected from 65. The system is in recording position.

The next step is to connect terminals 65 to one pair of terminals 68,69, 70 or 71, selectively. This is done in two steps in selectorsections 63 and 64. Section 63 connects terminals 65 to terminals 66 or67. Section 64 connects terminals 66 to 69 or 70 and terminals 67 to 68or 71. Assume a positive voltage on the grid of 57 and a negativevoltage on the grid of 58, then terminals 65 are connected to terminals67.

Section 64 comprises basically two sections 63, except that they arecombined into only two saturable reactor elements with only two controlwindings, instead of four elements. Assume a positive voltage on thegrid of 59 and a negative voltage on the grid 60, terminals 66 will beconnected to 70 and terminals 67 will be connected to 71. However, sincethere is no connection between 65 and 66, the connection is now madefrom 65 via 67 to 71 and magnetic head 45 for recording information ondrum 49.

A positive voltage on the grid of 55 and negative voltage on the grid of56 will-cause the recorded signal .to be reproduced and appear atterminals 53.

Fig. 10 illustrates how a number of selectors of the type of Fig. 8 canbe combined into a single selector unit with only two saturable reactorunits. This selector comprises two saturable reactor elements v and 81,,each having a saturable core 82 and 83, and a control winding 84 and 85,respectively. This selector connects selectively each one of five firstterminals 86, 87, '88, 89 and 90' to one of two pairs of secondterminals, there being a total of ten pairs, numbered 91 through 100. Ifcontrol winding 84 is energized while no current flows through 85, allterminals 86, 87, 88, 89 and 90 are connected to terminals 91, 92, 93,94 and 95, respectively. Inspecting terminals 86, 91 and 100, andconnecting controlled windings, it is seen that controlled 'windings1'01, 102 and 103 form the same series and shunt network betweenterminals 86 and '91 as shown in 'Fig. 8. Similarly, windings 104, 105and 106 form a network between terminals 86 and 100. The same types ofnetwork are formed between other terminals. Obviously, similar selectorscan be built for any number X of pairs of first terminals and 2X pairsofsecond terminals.

Fig. 11 shows how various selector units can be combined into a decimalselector system. This system comprises sections 110, 1 11, 112 and 113,with one pair of first terminals 114 and ten pairs of second terminals115. Each section has two control windings, their terminals indicated bynumeral 116. Sections 110 and 111 are as shown in Fig. 8. Section 112 isthe same as shown as section 64 of Fig. 9, while section 113 is shown indetail in Fig. 11.

Of the two pairs of second terminals of 110, one pair is connected tosection 111, and can be selectively connected to any one of four of thefive pairs of first terminals of section 113. The remaining pair ofterminals is connected directly to one of the second terminals ofsection 110. By properly energizing and deene'rgizing control windingsof the various sections, terminals 114 can be connected to any one pairof terminals 115.

Because of the attenuation of energy sutfered by transmission throughsections 111 and 112, as contrasted to the absence of attenuation in thedirection between sections 110 and 113, section 110 is madeunsymmetrical, that the attenuation of 111 and 112 are built into one ofthe networks. In this manner energy transmitted between 114 and any pairof terminals 115 suffers the same attenuation regardless of directconnection between sections 110 and 113 or transmission by way ofsections 111 and 112.

Fig. 12 shows a selector system comprising selector units to 126, eachas shown in Fig. 8. These units are arranged in N=3 tiers, the systemhaving a pair of first terminals 127 and 2 =8 pairs of second terminals128. Each unit has one pair of first terminals and two pairs of secondterminals. Each tier has 2 pairs of first N terminals and 2 pairs ofsecond terminals. Second terminals of one tier are connected to firstterminals of the next higher order tier. Each unit has a pair of controlwindings, whose terminals are indicated for unit 120 as 130 and 131. Thenetworks of controlled windings in the units, can be exactly the same asin Fig. 8, or of any other suitable design employing more or fewercontrolled windings, as will be obvious to those skilled in the art,Without departing from the spirit of my invention.

This system has the advantage of using identical units, but has thedisadvantage of requiring seven separate pieces of information, toenergize seven and deenerg'ize another seven associated controlwindings.

Fig. 13 shows another system for accomplishing the same purpose, usingthree selector units 140, 141 and 142, that is only one unit per tier.Unit is of substantially the same designas shown in Fig. 8. Unit 141 isof the same design as section 64 of Fig. 9. Unit 142 is of the samedesign as shown in Fig. 10, except for omission of one pair of firstterminals and associated two pairs of second terminals as Well asassociated controlled windings. For example, unit 142 is obtained fromFig. 10 by omitting terminals 86, 91 and 100, as Well as windings 101 to106, inclusive.

The system has a pair of first terminals 143 that can be selectivelyconnected to any one pair of second terminals 144 by selectivelyenergizing and deenergizing the appropriate control windings of eachunit. Each unit and each tier has two control windings, the terminalsfor unit 140 being indicated at 145 and 146.

This system has the advantage of requiring only three pieces ofinformation, to energize three and deenergize another three associatedcontrol windings. It has the disadvantage of requiring three difierenttypes of selector units.

While I have illustrated and described the best form of embodiment of myinvention now known to me, it will be apparent to those skilled in theart that changes may be made in the form of the apparatus disclosedwithout departing from the spirit of my invention as set forth in theappended claims, and that in some cases certain features of my inventionmay be used to advantage without corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. An electrical switch comprising a pair of first terminals and a pairof second terminals, a first and second mechanically static electricalreactance element, said elements exhibiting non-linear controllablereactance characteristics, control means associated with each of saidelements for varying the magnitudes of said reactances, an electricalcircuit path, between said first and said second pairs of terminalsincluding said first element in series relation to said circuit path andsaid second element in shunt relation to said circuit path, and circuitmeans including said control means for selectively effectingsimultaneous increase of the reactance of one of said elements anddecrease of the other of said elements, thereby to control theelectrical impedance between said first and second pairs of terminals.

2. An electrical switch comprising a pair of first terminals and a pairof second terminals, a first plurality and a second plurality ofmechanically static electrical reactance elements, said elementsexhibiting non-linear controllable reactance characteristics, firstcontrol means associated with said first elements for simultaneously andidentically controlling the reactances of said first elements, secondcontrol means associated with said second elements for simultaneouslyand identically controlling the reactances of said second elements, anelectrical network connecting said first and second pairs of terminalsincluding said first elements in series relation to said pairs ofterminals and said second elements in shunt relation to said pair ofterminals, and circuit means including said control means for electivelyeffecting simultaneous increase of the reactance of one plurality ofelements and decrease of the reactance of the other plurality ofelements, thereby to control the electrical impedance between said firstand second pairs of terminals. I

3. An electrical switch comprising a pair of first circuit points ofreference and a pair of second circuit points of reference, av first andsecond mechanically static electrical aperiodic reactance element, saidelements exhibiting non-linear controllable aperiodic reactancecharacteristics, control means associated with each of said elements forvarying the magnitudes of said reactances, electrical circuit pathsbetween said first and said second pairs of circuit points of referenceincluding substantially solely said first element in series relation tosaid circuit points of reference and said second element in shuntrelation to said circuit points of reference, and circuit meansincluding said control means for selectively efiecting simultaneousincrease of the reactance of one of said elements and decrease of thereactance of the other of said elements, thereby to control theelectrical impedance between said first pair and said second pair ofcircuit points of reference.

Progress Report No. BL3 of the Computation Labo ratory, Harvard Univ.,by Robert C. Minnick (pages 5.6, 5.13-5.16, and 5.18 relied upon).

